DeFi (or defi) simply means decentralized finance and describes any blockchain software that has to do with finances. Decentralized finance (DeFi) refers to an alternate finance system that uses public blockchain technology for performing all kinds of financial activities.

Have you ever seen old monochrome pictures (most often grayscale) which have several artefacts, that are then colorised and made to look as if they were taken only recently with a modern camera? That is an example of image restoration,